1. Field of the Invention
The present invention relates to an apparatus and method for dispensing products, such as agricultural products, over a field.
2. Description of the Prior Art
When dispensing agricultural products (lime, fertilizer, etc.), it has heretofore been difficult if not impossible to attain a very high degree of uniformity in applying these products to a broad area. Typically, agricultural products are applied in large quantities using a spreading apparatus having one or more holding bins with an auger shaft running horizontally in the bottom of the holding bin to dispense the product through one or more exit ports. A tractor generally is used to pull the dispensing device, and the motive force for rotating the auger shaft which causes the product to be dispensed is provided by a hydraulic system having a fluid reservoir connected to a hydraulic motor by hydraulic lines. The problem has arisen in that while the linear rate of travel of the tractor pulling the spreading apparatus may be constant, the speed of the hydraulic motor, and therefore the speed at which the auger shaft is driven, varies considerably from time to time during the application of a single product over a particular field. The speed with which the hydraulic motor drives the auger shaft varies due to changes in viscosity in the hydraulic fluid. The speed of the motor, and therefore the shaft, typically increases with longer periods of operation, since as the hydraulic fluid warms up the motor will increase its output accordingly. With changes in the temperature of the hydraulic fluid, the motor's output and the shaft's rotational speed will vary accordingly. This results in an uneven distribution of the product applied, which may often result in reduced crop yields, as well as waste of the product and therefore increased costs.
A search of the U.S. patent literature disclosed a number of devices for dispensing agricultural products. For example, a mechanism to permit a tractor driver to monitor the application of seeds and count the number of seeds dispensed is disclosed in U.S. Pat. No. 3,422,776, Gregory, Jr. The device also indicates the distance traversed by the planter mechanism so that the operator may correlate the number of seeds dispensed with the distance traversed in order to determine whether or not a proper rate of feed is being obtained. An odometer which permits a tractor operator to measure the acreage planted as it is being planted is shown in U.S. Pat. No. 3,137,073, Rawlinson, so that the farmer may measure the amount of acreage planted in order to conform to crop-acreage control laws of particular crops. This apparatus shows a conventional odometer is mounted on the frame of a planter with a lever arm adapted to be rotated by a finger mounted on the end of the planter axle. U.S. Pat. No. 2,099,369, Lutz, shows an auger shaft disposed within a holding bin such that lime is dispensed therefrom.
With regard to various devices which measure rotation of a shaft or other objects, a number of patents were noted. U.S. Pat. No. 3,779,456, Burnett, shows an attachment for a motor vehicle wheel which clamps to the rotating hub of the wheel. There is a shaft which rotates with the vehicle wheel and about which a weighted counter body depends to count and record the revolutions of the shaft. U.S. Pat. No. 3,598,309, Ingler, shows a "driveless" odometer adapted to be mounted on the hubcap of a vehicle wheel. There is a signalling device adapted to be operated upon completion of a predetermined number of revolutions of the rotating member in order to attract the attention of the vehicle operator to perform a particular function, such as to change the motor oil after a particular number of revolutions.
To the best knowledge of the applicant, all of the devices shown in the above patents have various shortcomings in providing a truly satisfactory system for uniformly spreading an agricultural product.
One possible approach which the applicant considered in arriving at the present invention was to monitor the rate of application of the product by relating this to the rotational speed of the auger shaft, and then monitor the speed of the auger shaft relative to the rate of travel of the dispensing vehicle. However, attempts to accomplish this were initially frustrated due to the fact that the auger shaft does not rotate perfectly about a linear longitudinal axis, either because the bushings and bearings used to mount such shafts in agricultural implements fail to maintain even a true shaft rotating about a linear axis, and conventional devices such as odometers, would not properly measure the rate of rotation. This problem was eventually solved in providing the system of the present invention.
It is an object of the present invention to provide an apparatus and method which enables the uniform dispensing of a product, such as an agricultural product, over a field.